Bending machine

ABSTRACT

A tube bending machine having the capability of releasing the tube from the carriage for longitudinal movement during bend formation, while maintaining a plane of bend reference. The end of the tube is connected with a rod extending through the carriage collet. The rod has a non-round cross-section and extends through a mating adapter on the carriage which permits relative longitudinal movement while preventing relative rotation between them.

United States Patent Sindelar [451 Aug. 22, 1972.

[54] BENDING MACHINE [72] Inventor: Ernest C. Sindelar, Sugar Grove,111.

[73] Assignee: Pines Engineering Co., Inc.

[22] Filed: Feb. 25, 1970 [21] Appl. No.: 13,982

52 us. Cl. ..72/311, 72/156, 72/369, 72/422 51 Int. Cl. ..B2ld 11/04[58] Field of Search ..72/156, 293, 311, 318, 250, 72/369, 422, 149,150, 298, 301, 10, 14, 23,

[56] References Cited I UNITED STATES PATENTS 3,553,989 l/l971 Munro eta1. ..72/8 2,306,223 12/ 1942 Parker et a1. ..72/ 150 3,336,776 8/1967Zerlaut ..72/14 3,475,938 11/1969 Whitney, Jr. et a1. ..72/159 3,426,5622/ 1969 Inda ..72/24 2,312,121 2/1943 Parker et a1. ..72/156 PrimaryExaminer-Charles W. Lanham Assistant Examiner-Michael .1 KeenanAttorney-Hofgren, Wegner, Allen, Stellman & Mc- Cord [57] ABSTRACT Atube bending machine having the capability of releasing the tube-fromthe carriage for longitudinal movement during bend formation, whilemaintaining a plane of bend reference. The end of the tube is connectedwith a rod extending through the carriage collet. The rod has anon-round cross-section and extends through a mating adapter on thecarriage which permits relative longitudinal movement while preventingrelative rotation between them.

7 Claims, 4 Drawing Figures 'BENDING MACHINE This invention is primarilyconcerned with a means for maintaining the validity of a bend angleplane in a tube bender without clamping or securing the work to alongitudinal positioning mechanism during the bending operation.

In a rotary tube bender, for example, a length of tube is held at oneend, as by a releasable collet, on a movable carriage. The tube extendsalong a rotary die against which it is clamped during the bendoperation. A pressure die is held against the tube during rotation ofthe bending die to cause formation of the bend without excessivedeformation of the tube.

Prior to the bending operation the collet is clamped to the tube, andthe carriage moves the tube to the desired bend position and rotates thetube with respect to the plane of the bend arm to the desired bend angleplane. During the bending operation the collet may be clamped to thetube to cause it to move with the car riage, or may be released so thatthe carriage and tube collet is clamped or released. If the collet isreleased during the bending operation the tube may rotate with respectto the plane of the bend arm thereby preventing the production of thedesired bend angle plane. This is particularly a problem where it isdesired to maintain an accurate bend plane reference during the bendingoperation. If the collet is not released during the bending operation,the carriage is pulled forward as the bend is made, a tube having a lowelastic limit will be deformed or stretched. The amount of strainproduced will depend upon such factors as tube diameter, wall thickness,elasticity, temper, and tensile strength of the material, and the like.Occasions will arise where the above characteristics of the work aresuch that the amount of strain introduced is excessive resulting in animpermissible amount of error in the finished tube dimensions. Thepresent invention provides a means, other than clamping the tube in thecollet, to prevent tube rotation during the bending operation whereneither of the above two types of dimensional errors is allowable.

The principal object of this invention,,therefore, is to provide animproved means for preventing tube rotation in a tube bender during thebending operation.

Another object of this invention is to provide means to prevent tubestrain while maintaining the validity of the bend plane angle during thebending operation in a tube bender as described above. I

A further object of this invention is to make such an aforementionedrotation prevention means readily mountable on and removable from thebending machine.

Still another object of this invention is to provide such an improvedrotation prevention means adaptable for use with tubes of various sizesor tubes with various shaped end fittings.

Other objects, features, and advantages of this invention will readilybe apparent from the following specification and from the accompanyingdrawings of which:

FIG. 1 is a diagrammatic plan view of a rotary tube bender at the startof a bend showing the relative position to the carriage, rod, shaft, andguide means;

FIG. 2,is a fragmentary diagrammatic plan view of the guide means andguide mounting means taken generally along line 3-3 of FIG. 1; and

FIG. 4 is an enlarged sectional view of the guide means taken generallyalong the line 44 of FIG. 3.

In the drawings and in the following description there is disclosed onlyso much of the bending machine'that is directly pertinent to theinvention. The bending machine has a base 10 on which carriage l l ismounted for longitudinal and rotary movement. The carriage 11 includesclamp means 12 in which a length of tube 13 to be bent is carried. Clampmeans 12 may be clamped to tube 13 to cause it to move with carriage 11,or may be released so that carriage 11 and tube 13 may moveindependently.

The bending tools include a rotary bending die 14, a tube clamp 15, anda pressure die 16. Bending die 14 has a groove 14a in the side wallthereof with a depth slightly less than the radius of tube 13. The diehas a semi-circular peripheral portion 14b at the left (as shown inFIG. 1) with two parallel straight sided sections 14c tangent thereto.The bending die is rotatable about the axis of shaft 17 with whichsemi-circular end portion 14b is concentric. Clamp 15 has an end portion150, also with a tube receiving groove therein, which holds the tubeagainst the straight sided portion 140 of the bending die. The clamp ismovable toward and I away from the bending die. Clamp 15 is mounted onend of a 90 bend. Bend arm 18, bending die 14 and tube clamp 15 havemoved to an arc of 90 and tube bend;

clamp 15 holds tube 13 against bending die 14. Pressure die 16 has movedin a straight line a distance equal to the arc of the bend and stillholds the trailing edge of tube 13 straight and against the peripheralportion of the bending die 14a.

In normal course of bending operation (previous to this invention) astraight tube l3 is inserted through clamp means 12 on carriage 11 andcarriage 11 is moved longitudinally to position tube 13 at theappropriate point for the start of a bend at the tangent point betweenthe semi-circular 14a and straight 14b portions of bending die 14. Atthe same time, carriage 11 rotates (if necessary) so that the plane ofthe bend is properly related to the previous bend or to a particularorientation of an end fitting on tube 13. When the tube is positionedfor the bend, carriage 11 stops and tube clamp 15 and pressure die 16close, and the bend is formed. During the bend, clamp means 12 isreleased, the tube end is loosely received in clamp means 12, and theportion of tube 13 used in forming the bend is drawn out. When the bendis completed, clamp means 12 is reclosed, and tube clamp 15 and pressuredie 16 are released, providing suflicient clearance for tube 13 to move.Carriage 11 then positions the tube 13 for a new bend. The difficultyencountered with the above approach is that during the bending operationwhen clamp means 12 is released tube 13 may rotate so that the plane ofa subsequent bend may not be properly related to the plane of the firstbend.

An alternate approach may be used, where during the bending operationclamp means 12 on carriage 11 is not released and the carriage movesforwardly with tube 13 and while tube 13 is wrapped around bending die14. The difficulty encountered using this approach is that if thetensile strength of the tube is sufficiently low the tube will stretchexcessively from the drag of the carriage.

In particular the problem has been encountered in bending a smalldiameter coaxial cable having a connector fitting at one end whichrequires precise angular orientation. Using the present inventiondescribed herein, both of the above aforementioned problems areresolved. In the present invention (FIG. 1) the tube 13 is connected toelongated rod 22 by tube connector 20. The elongated rod 22 extendsthrough clamp means 12. Elongated rod 22, in turn, is connected tonon-circular shaft 14 by rod connector 16 (FIG. 3). Non-circular shaft24 extends through guide means 28 which is mounted in the end of tubularmember 30, at the rear of carriage l 1.

Referring now to FIG. 4, a cross-section of a particular embodiment ofthe guide means 28 is shown. In this embodiment the guide meanscomprises outer surface 42, inner cylindrical surface 44, and aplurality of rotatable ball bearings 46 carried by and projectinginwardly from inner cylindrical surface 44. The non-circular shaft 24has a plurality of splines 50 extending into the spaces between ballbearings 46. Non-circular mating surface 52 of shaft 24 with ballbearings 46 and inner cylindrical-surface 44, prevents relative rotationbetween guide means 28 and splined shaft 48, while the rotatable ballbearings 46 allow and enhance freedom of relative longitudinal movementbetween guide means 28 and splined shaft 48.

A movable shaft stop means 40 is mounted on non circular shaft 24 so asto prevent shaft 24 from inadvertently sliding through the guide means28. Although a particular embodiment of the guide means and shaft meansis herein disclosed, it should be noted that any non-circular shaft 24extending through guide means 28 and mating therewith will serve equallyas well.

Utilizing the present invention, after the guide means is mounted andthe shaft, rod, and tube are secured, the normal course of a bendingoperation would be as follows: tube 13 is secured to connector 20 on therod 22; rod 22 is secured to carriage 11 by clamp means 12; carriage 11is moved longitudinally and rotationally to the desired position for thebend; clamp means 12 is released and the bending operation is performed.

Since during the actual bending operation, the clamp means 12 isreleased, tube 13 is allowed to move longitudinally carrying rod 22 andshaft 24 with it. However, shaft 24 prevents relative rotation betweencar riage 11 and tube 13, maintaining the desired angular reference, Atthe end of a bend operation clamp means 12 is reclosed, again securingrod 22 and hence tube 13 to carriage 11. The carriage can then move thetube to a new bend position.

Guide means housing 31 has threaded extension 32 on which is threadedshoulder means 33, expandable circular ring 34,and threaded collar 36.Guide means 28 is secured to tubular member 30 when threaded collar 36is tightened against shoulder means 33, thereby compressing expandablecircular ring 34 against shoulder 33, expanding it outwardly to gripinner wall 38 of tubular member 30.

The foregoing detailed description has'been given for clearness ofunderstanding only and no unnecessary limitation should be understoodtherefrom as some modification will be obvious to those skilled in theart.

I claim: 1. In a tube bender having a tube clamp, bend arm, and anelongated carriage with clamp means, said car riage being movablelongitudinally to position the tube with respect to said tube clamp androtatable to position the tube with respect to the plane of the bendarm, means for preventing rotation of the tube during the bendingoperation, comprising:

an elongated rod extending through said clamp means and having means forsecuring the tube thereto; and

means for preventing rotational movement of said rod with respect tosaid carriage while allowing the rod to be drawn from said carriage andclamp means during the bending operation.

2. The tube bender of claim 1, wherein said rotation preventing meanscomprises: a guide means secured to said carriage; and a non-circularshaft secured to said rod, with said shaft extending through said guidemeans and mating therewith, preventing relative rotation and allowingrelative longitudinal movement between the guide means and thenon-circular shaft.

3. The tube bender of claim 2, wherein said non-circularv shaftcomprises, a shaft with longitudinal splines extending along the lengththereof.

4. The tube bender of claim 3, wherein said guide means comprises: ahousing with inner and outer cylindrical surfaces mounted coaxially withthe carriage, and a plurality of rotatable ball bearings carried by andprojecting inwardly from said inner cylindrical surface.

5. The tube bender of claim 2, wherein said guide means has mountingmeans for temporary mounting on said carriage.

6. The tube bender of claim 5 in which said carriage includes a tubularmember having an end in which said guide means is mounted, said guidemeans including an expandable ring seated against a shoulder and athreaded collar movable to compress said ring against said shoulder andexpand it outwardly to grip the inner wall of the tubular member of saidcarriage.

7. The method of performing a bending operation with a tube benderhaving a bending mechanism and a carriage with tube clamp means thereon,movable longitudinally and rotatably to position a tube with respect tosaid bending mechanism, comprising:

connecting the tube to a rod free to move longitudinally with respect tothe carriage and restrained against movement rotationally with respectthereto;

securing said tube to said carriage by said clamp means, for movementtherewith;

longitudinally moving said carriage to position said tube with respectto said bending mechanism; rotating said carriage to orient said tubeangularly with respect to said bending mechanism;

securing said tube in said bending mechanism;

opening said tube clamp means on the carriage to release said tube forlongitudinal movement with respect to said carriage, the connection ofthe tube to said rod maintaining the angular reference between the tubeand the carriage;

performing the bending operation;

closing said clamp means; and

positioning said tube for the next bending operation.

1. In a tube bender having a tube clamp, bend arm, and an elongatedcarriage with clamp means, said carriage being movable longitudinally toposition the tube with respect to said tube clamp and rotatable toposition the tube with respect to the plane of the bend arm, means forpreventing rotation of the tube duRing the bending operation,comprising: an elongated rod extending through said clamp means andhaving means for securing the tube thereto; and means for preventingrotational movement of said rod with respect to said carriage whileallowing the rod to be drawn from said carriage and clamp means duringthe bending operation.
 2. The tube bender of claim 1, wherein saidrotation preventing means comprises: a guide means secured to saidcarriage; and a non-circular shaft secured to said rod, with said shaftextending through said guide means and mating therewith, preventingrelative rotation and allowing relative longitudinal movement betweenthe guide means and the non-circular shaft.
 3. The tube bender of claim2, wherein said non-circular shaft comprises a shaft with longitudinalsplines extending along the length thereof.
 4. The tube bender of claim3, wherein said guide means comprises: a housing with inner and outercylindrical surfaces mounted coaxially with the carriage, and aplurality of rotatable ball bearings carried by and projecting inwardlyfrom said inner cylindrical surface.
 5. The tube bender of claim 2,wherein said guide means has mounting means for temporary mounting onsaid carriage.
 6. The tube bender of claim 5 in which said carriageincludes a tubular member having an end in which said guide means ismounted, said guide means including an expandable ring seated against ashoulder and a threaded collar movable to compress said ring againstsaid shoulder and expand it outwardly to grip the inner wall of thetubular member of said carriage.
 7. The method of performing a bendingoperation with a tube bender having a bending mechanism and a carriagewith tube clamp means thereon, movable longitudinally and rotatably toposition a tube with respect to said bending mechanism, comprising:connecting the tube to a rod free to move longitudinally with respect tothe carriage and restrained against movement rotationally with respectthereto; securing said tube to said carriage by said clamp means, formovement therewith; longitudinally moving said carriage to position saidtube with respect to said bending mechanism; rotating said carriage toorient said tube angularly with respect to said bending mechanism;securing said tube in said bending mechanism; opening said tube clampmeans on the carriage to release said tube for longitudinal movementwith respect to said carriage, the connection of the tube to said rodmaintaining the angular reference between the tube and the carriage;performing the bending operation; closing said clamp means; andpositioning said tube for the next bending operation.